Selective dorsal rhizotomy (SDR) is a neurosurgical procedure advocated for the relief of spasticity in cerebral palsy (CP). Despite a lack of critica studies to document the clinical effectiveness of SDR, the procedure is being adopted enthusiastically. No published studies take into account the effect of possible selection bias, expectation bias or cotreatment. All children who undergo SDR also receive intensive physical therapy. The opportunity for objective study will be lost once SDR becomes broadly accepted, we propose a prospective randomized clinical trial using objectiv outcome measures to investigate the effectiveness of SDR. The purpose of this proposed study is to evaluate the effectiveness of SDR in reducing spasticity and improving gross motor function of children with spastic diplegia, a common form of CP. Eighty children, 3 - 18 years, will be recruited and randomized into two groups. Group A will receive SDR and intensive physical therapy for six months. Group B will receive equivalent intensive physical therapy but not SDR. Outcomes will be assessed blindly at entry, 6, 12, and 24 months. Outcome variables are: 1) electromechanica measurement of joint torque for spasticity, and 2) a valid objective clinical evaluation of gross motor function. Primary emphasis will be on 2 month outcome. Subject entry will be complete after 24 months and the last data collection will occur at 48 months. Data analysis and presentation will require a fifth year.